The micro pore system in source rocks is an important pathway for the primary migration of petroleum, and it is also an important storage space for the residual petroleum. In this paper we try to measure the micropores with different diameters by using gas adsorption and mercury injection methods, and analysis the distribution of micropores systemly. Experiment results indicate that the pore types in the source rocks of the first member of the Qingshankou Formation are mainly micro pores and meso pores. The distribution of pore volumes ranges from 1.8mL/mg to 30 mL/mg with a mean value of 9.49 mL/mg. The specific surface area rangs from 0.91m2/g to 31.02m2/g with a mean value of 7.02 m2/g. The source rock porosity is low, ranging from 1.2% to 3.87% with an average value of 2.17%. The content of organic matters (OM), illite and pyrite and pore volume shows positive correlation. It is believed that the diameters and abundance of micro pores will increase with the increasing content of the three minerals mentioned above; but the content of chlorite in clay minerals and quartz, calcite and anorthose in non clay minerals and pore volume shows negative correlations. The data shows that the diameters and abundance of micro pores decrease with these three minerals' contents. The content of kaolinite and pore volume show a negative correlation, it means that the micro pore in source rocks may be not affected by kaolinite. In addition, the development and distribution of micro pores in source rocks are also affected by the types, abundance, thermal evolution degree of organic matters, arrangement of clay minerals, secondary change of non clay minerals.